Control system



c. F. CZERNEK CONTROL SYSTEM March 7, 1967 Ori inal Filed Aug.

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CONTROL SYSTEM Original Filed Aug. 5, 1965 6 Sheets-Sheet 5 J71 Z/fliifCzydergjernek March 7, 1967 C, F. CZERN'EK 3,307,584

CONTROL SYSTEM Original Filed Aug. 5, 1963 6 Sheets-Sheet 6 1710675557:C dgffqjefrzek United States Patent 3,307,584 CONTRDL SYSTEM Clyde F.Czemek, Sepulveda, Calif., assig or to Weston Hydraulics, Limited, VanNuys, Califl, a corporation of California Original application Aug. 5,1963, Ser. No. 299,969, now Patent No. 3,229,588, dated Jan. 18, 1966.Divided and this application Oct. 22, 1965, Ser. No. 525,780 6 Claims.(Cl. 137625.64)

The present application is a division of application Serial No. 299,969,filed August 5, 1963, now Patent No. 3,229,558 granted January 18, 1966,entitled Control System.

This invention relates to a control system for an actuator and moreparticularly to a servo control system.

Briefly described, the invention includes a novel hydraulic digitalconverter which in turn includes a plurality of cylinder-piston addersarranged in series. Each cylinder-piston adder is actuated independentthe adjacent cylinder-piston adders. The first adder in the seriesreacts against a fixed reference point and as a given piston extends orretracts within its cylinder, the length of the series of adders changesa corresponding amount. The total movement of the adder assembly is thusdetermined by the combined cumulative displacements of the pistons withrespect to their respective cylinders. A novel combination ofcylinder-piston displacements plus a unique mode of actuating theindividual adders makes the hydraulic digital converter especiallysuitable for use in a servo system. The servo system may include afeedback linkage from the actuator to the hydraulic digital converter.

A more complete understanding of the invention will be readily apparentto those skilled in the art from the specification and appended drawingillustrating a certain preferred embodiment in which:

FIGURE 1 is a schematic representation of one embodiment of the servocontrol system;

FIGURE 2 is a view, partially in cross section, illustrating theactuator and its associated relationship with the servo system;

FIGURE 3 is a view, partially in cross section, taken generally alonglines 3-3 of FIGURE 2;

FIGURE 4 is a view, partially in cross section, taken generally alonglines 4-4 o-f FIGURE 2;

' FIGURE 5 is a partial view, partially in cross section, of the digitalconverter component and the control valve component of the servo system;

FIGURE 6 is a view, partially in cross section, illustratin-g thehydraulic digital converter component of the servo system;

FIGURE 7 is a view, partially in cross section, taken generally alonglines 77 of FIGURE 6;

FIGURE 8 is a view, partially in cross section, taken generally alonglines 88 of FIGURE 6; and

FIGURE 9 is a schematic representation of an alternate embodiment of theservo control system.

Referring now to the drawing and more particularly FIGURE 1, theactuator housing 20 is provided with opposed openings 22 and 24. Anactuator piston rod 26 extends through the openings 22 and 24. Thepiston rod 26 includes a first end 28 reciprocally received within aground member 30 of the actuator housing. The ground member 30 isadapted to be pivotally connected to ground by way of pivot hole 32. Theactuator piston rod 26 carries an actuator piston 34 which is locatedwithin the chamber 36 of housing 20'. Ports 38 and 40 communicate withchamber 36 on opposite sides of the actuator piston 34.

A flow control valve 42 is provided to direct fluid under ice pressurefrom a source of fluid underpressure to chamber 36 and to direct fluidfrom chamber 36 to a return line. The flow control valve 42 includes abore 44, spool 46 and ports 48, 50, 52, 54 and 56. The spool includeslands 58 and 60 as well as feedback end 62 which is connected tofeedback link 64. An inlet passage 66 is connected to a source of fluidunder pressure and is arranged to supply fluid under pressure to port 48which port is located intermediate lands 5860 in bore 44. An outletpassage 68 is adapted to communicate ports 50-52 with a fluid returnline. Port 50 is positioned in the bore 44 between land 58 and the leftend of the bore 44 and port 52 is positioned in the bore 44 between land60' and the right end of bore 44.

The digital converter 70 includes an elongated bore 72 having an opening74 at one end thereof. A plurality of adders 76 is provided within thebore 72. Each of the adders 76 includes a cylinder 78 slida-blypositioned within the bore 72. Each cylinder 78 is provided with spacedapart lands 80 which provide sealing contact between their respectivecylinders and the bore 72. Each of the cylinders is provided with achamber 82 and an opening 84 extending from the chamber '82 to theexterior of the cylinder 78. The cylinders include a port 86 which islocated intermediate the spaced apart lands 80. The port providescommunication between the bore 72 and the chamber 82. An adder piston 88is provided within each chamber 82. Each of the adder pistons includesan adder piston rod 90 which extends through passage 84 into the bore72.

The adders 76 are preferably arranged in series in a manner such thatenergization of an adder with the resultant movement of the individualpiston with respect to its associated cylinder (its stroke) results inthe elongation of the total series of adders by an amount equal to thestroke of the cylinder-piston adder. In other words, a movement of anindividual piston through its stroke (a predetermined distance) withrespect to its cylinder results in the same displacement of therespective ends of the cylinders of the total adder series.

A biasing means 92 is provided at one end of the bore 72. The biasingmeans includes a biasing cylinder 94 having spaced apart lands 96a and9612 on the exterior surface thereof which lands form a seal with thebore 72. The biasing cylinder 94 includes an internal chamber 98 and anopening 100 extending into the bore 72. A piston 102 is reciprocablymounted within the internal chamber 98. The piston includes a piston rod104 extending through the opening 100 into the bore 72. A port 106 isprovided through the wall of the biasing cylinder 94 between the spacedapart lands 96a and 96b. The primary function of the biasing means 92 isto collapse the series of adders (cause the pistons to retract withintheir cylinders) in the absence of fluid under pressure being suppliedto the individual adders. System pressure is fed to bore 72 by way ofport and acts against land 96a to force biasing cylinder 94 to theright. The force exerted by system pressure in an individual adder issuflicient to overcome the force exerted by system pressure acting onland 96a. A restrictor 97 is located in port 105. The purpose of therestrictor is to control the re- .action speed of the complete set ofadders. This is necessary to minimize the retrograde, or reversal instroke, which can occur due to differences in actuation time of theindividual adder. The biasing cylinder 94 includes an end portion 108which extends through the opening 74. The end portion 108 is adapted tobe connected to the feedback link 64 by way of pin 110. The disclosedbiasing means is of the hydraulic type; however, it will be readilyapparent to those skilled in the art that other biasing means may besubstituted as a means of collapsing the adders. Likewise, theconnection between the digital converter and the feedback link has beenillustrated as connected to the biasing means. Substantially similarresults may be achieved by connecting the feedback link directly to theadder series.

where P=number of positions and n number of cylinder-piston adders. Atypical program utilizing the embodiment illustrated in FIGURE 1 isgiven in the following table:

TABLE I.SERVO SYSTEM CODE Solenoid Nos.

Position No. Actuator Position Solenoid Nos. Position No. ActuatorPosition MMMMM X denotes solenoid-adder as actuated.

An important characteristic of the individual adder is the fact that ithas two operating positions; one of which is with the piston fullyretracted, and the other of which is with the piston fully extended.Another important characteristic of this arrangement of adders is thatthe stroke of the series of adders is equal to the sum of the stroke ofthe individual adders.

Individual independent input signal means 112 is provided to admit fluidfrom the pressure source to each of the adders. The input signal meansdisclosed in FIGURE 1 includes a plurality of solenoids 114 which admitfluid from the inlet passage 66 through valves .116 and passages 118 tothe bore 72 intermediate the lands 80 of the cylinders 78 of theindividual adder assemblies. These solenoids 114 further provide for therelease of fluid from the chambers 82 by way of passages 118, and valves120 to exhaust pressure by way of outlet passages 68.

A polarity adder 122 includes a solenoid 124 and valve 126 with seats125 and 127. Valve .126 is adapted to assume two positions; the first ofwhich admits fluid from the supply source by way of the passage 66 andpassage 128 to bore 72 intermediate lands 66 on the biasing cylinder 94and port 106 into the internal chamber 98 of the biasing cylinder 94,and the second of which admits fluid from the internal chamber 98, port106 and passage 128 into outlet passage 68.

A particularly important feature of the present invention is the strokeof each individual adder with respect to the stroke of the other adders.A preferred arrangement is with the stroke of the first adder in theseries of a predetermined length and each additional adder in the serieswith a stroke equal to two times the stroke of the preceding adder.These strokes can be set for any value compatable with the code beingused. The number of cylinder-piston adders used in the series determinesthe maximum number of positions which can be selected. With the,preferred relationship of relative strokes set forth hereinabove, themaximum number of control positions is governed by the formula:

FIGURE 9 illustrates an alternate embodiment of a control systemutilizing an actau-tor A, a four-way valve V, a digital converter DC, afeedback linkage F, input signal means S and a resilient biasing meansB. This embodiment utilizes a resilient biasing means to collapse theindividual adders upon de-energization of their respective solenoids.This biasing means is used in lieu of the hydraulic biasing meansdisclosed in FIGURE 1. This alternate embodiment also differs from theFIGURE 1 embodiment in that the feedback link is connected to the adderassembly.

Referring to FIGURE 1 and the operation of the system, fluid underpressure is supplied by way of inlet passage 66 to port 48, valve 116,valve 126, and port 105. Assuming valves 116 are closed and valve 126 isseated on seat 127, fluid under pressure from inlet passage 66 is fed tobore 72 by way of port and this fluid acts against land 96a to shift thebiasing cylinder 94 to the right, thus collapsing the individual adderassemblies. Energization of an individual solenoid 114 causes valve 116to open and valve to close. This admits fluid from inlet passage 66 topassage 118, and bore 72 intermediate lands 80. This fluid passesthrough port 86 into the adder chamber 82, thus causing the adder piston88 and the adder cylinder 78 to shift with respect to each other suchthat the adder piston rod 90 is fully extended. As each additionalsolenoid is energized, its respective valve members 116 and 120 operateas described here inabove and its associated cylinder-piston adderassembly is activated to extend the adder piston rod 90 from the end ofits cyplinder an amount equal to the stroke of the cylinder-pistonadder. As each adder is activated, the

. overall length of the series of adders is increased an ments willcomplete their travel in a shorter period of time than that required forthe longer stroke adders if each were subjected to the same pressure andflow conditions. The subject restrictors 117 are uniquely sized in sucha way that the resulting restrictors impose limitations on the pressureand flow being supplied by the solenoid valves 114 and 124 and henceequalize the actuation time of each of the individual adder assemblies.

An increase in length of the series of adders results in movement of endportion 108 to the left. This causes feedback link 64 to shift to theleft thus changing the position of the four-way valve spool 46. Land 58moves from a position blocking flow through port 56 thus allowing fluidunder pressure in bore 44 to pass through port 56, port 38 and intochamber 36 thus shifting the actuator piston 34 to the right. Land 60 ofspool 46 moves from a position blocking port 54 thus permitting flow offluid from chamber 36 through port 40 and bore 44 throughport 52 intooutlet passage 68. As the actuator piston 34 moves to the right,feedback link 64 carries the feedback end 62 of the valve spool to theright thus re-positioning lands 58 and 60 in a position blocking ports56 and 54, respectively.

The above procedure of operation is substantially reversed uponde-energization of the solenoid. For example, de-energization of thesolenoid causes valve 116 to close and valve 120 to open. This vents thefluid in chamber 82 through port 86, passage 118 and valve 120 to outletpassage 68. Fluid under pressure from inlet passage 66 is fed to bore 72by way of port 105 and this fluid acts against land 96a of biasingcylinder 94 thus shifting the biasing cylinder to the right. The biasingcylinder causes the deflating adder to collapse. This shortens theoverall length of the adder series and shifts the end portion 108 of thedigital converter to the right. Movement of the end portion 108 causesthe feedback link 64 to shift the feedback end 62 of the spool 46 t0 theright. Land 60 is moved from a position blocking flow through port 54thus permitting fiuid'to flow from port 48 through port 54 and port 40into the actuator chamber 36 thus shifting the actuator piston to theleft. At the same time, land 58 of spool 46 is moved from a positionblocking flow through port 56 thus permitting fluid to flow from chamber36 through ports 38, 56 and 50 into outlet passage 68 to exhaustpressure.

Movement of the actuator piston to the left carries feedback link 64 tothe left re-positioning feedback end 62 of the valve spool 46 such thatlands 60 and 58 block the flow of fluid through ports 54 and 56respectively.

The polarity adder which consists of biasing cylinder 94, piston 102 andits associated valve 126 provides for extreme simplification of thedigital program code for the servo system. The stroke of piston 102 withrespect to the biasing cylinder 94 is preferably at least equal to thecumulative stroke of all the other cylinder-piston adder units. With theprovision of the polarity adder, it is possible to de-energize all thecylinder-piston adder solenoids as Well as the polarity adder solenoidand obtain a null position of the piston actuator 34 at a substantiallycentral location within the actuator housing. Thus, with the polarityadder solenoid 124 de-energized, it is possible to obtain 32 separatepositions of the piston actuator on one side of null and with thepolarity adder solenoid energized it is possible to obtain 32 separatepositions of the piston actuator on the other side of null. Thisparticular digital code program,-utilizing the combination ofcylinder-piston actuators and solenoids as disclosed in FIGURE 1, ispreferable in that a loss of electrical power to the system results inpositioning the actuator piston at null rather than hard right or hardleft.

The servo system disclosed herein is capable of precise positioning andis suitable for use in aircraft and missile flight control surfaceactuation, missile nozzle gimbaling actuation, machine tool controls,and other control systems wherein digital incremental control isdesired.

Manifestly, the construction as shown .and described is capable of someadditional modification and such modification as may be construed tofall within the scope and meaning of the appended claims is alsoconsidered to be within the spirit and intent of the invention.

I claim:

1. A servo valve suitable for operating an actuator comprising a housinghaving a bore formed therein, a plurality of cylinders arranged inend-to-end relationship slidably positioned Within said bore forming aseries of cylinders, a piston reciprocally mounted within each saidcylinder, a piston rod associated with each piston extending from saidcylinder, an inlet passage within said housing adapted to receive fluidunder pressure, means con necting said inlet passage to said first boreto provide a bias against said series, means connecting said inletpassage to said first bore to provide for admission of fluid within eachsaid cylinder to cause reciprocation of said piston with respect to saidcylinder, a flow control valve suitable to direct fluid to and away fromsaid actuator, means connecting said inlet passage with said flowcontrol valve, means driven by said series of cylinders to actuate saidflow control valve, and an outlet passage interconnected with said flowcontrol valve and said first bore.

2. A servo valve comprising a housing having a first bore and a secondbore therein, a series of adders each including a cylinder with a pistonmounted therein reciprocally positioned within said first bore, means tobias said series in a manner to shorten the length of said series, inletpassage means to supply fluid under pressure to each said adder suchthat said piston and said cylinder are caused to move with respect toeach other to increase the length of said adder and said series, meansto control the rate of operation of each of said adders, a flow controlvalve positioned within said second bore, means providing communicationbetween said inlet passage means and said flow control valve, meansresponsive to the length of said series to shift said flow control valveand outlet passage means in communication with said flow control valveand to each said adder.

3. A servo valve comprising a housing having a first.

bore and a second bore therein, a series of adders each including acylinder with a piston mounted concentrically and reciprocally therein,said adders being reciprocally positioned within said first bore, meansto bias said series in a manner to shorten the length of said series,means to control the rate of operation of said series of adders, fluidinlet passage means effective to supply fluid under pressure to eachsaid adder such that said piston and said cylinder are caused to movewith respect to each other to increase the length of said adder and saidseries, means to control the rate of operation of each of said adders, aflow control valve positioned within said second bore, means connectingsaid fluid inlet passage with said flow control valve, means responsiveto the length of said series to move said flow control valve and fluidoutlet passage means connected with each said adder and said flowcontrol valve.

4. A servo valve comprising a housing having a first bore and a secondbore therein, a series of adders each including a cylinder with a pistonmounted therein reciprocally positioned within said first bore, meansresponsive to fluid under pressure to bias said series in a manner toshorten the length of said series, means to control the rate ofoperation of said series of adders, fluid inlet passage means effectiveto supply fluid under pressure to each said adder such that said pistonand said cylinder are caused to move with respect to each other toincrease the length of said adder and said series, means to control therate of operation of each of said adders, a flow control valvepositioned within said second bore, means connecting said fluid inletpassage with said flow control valve, means responsive to the length ofsaid series to shift said flow control valve and fluid outlet passagemeans connected with each said adder and with said flow control valve.

5. A servo valve comprising a housing having a first bore and a secondbore therein, a series of adders each including a cylinder With a pistonmounted therein reciprocally positioned within said first bore,resilient means to bias said series in a manner to shorten the length ofsaid series, fluid inlet passage means effective to supply fluid underpressure to each said adder such that said piston and said cylinder arecaused to move with respect to each other to increase the length of saidadder and said series, a flow control valve positioned within saidsecond bore, means interconnecting said fluid inlet passage with saidsecond bore, means responsive to the length of said series to shift saidflow control valve and fluid outlet means in communication with saidfirst bore and said second bore.

6. A servo valve comprising a housing having a first bore and a secondbore therein, a series of adders each including a cylinder With a pistonmounted the-rein reciprocally positioned Within said first bore, meansto bias said series in a manner to shorten the length of said series,means to control the speed of operation of the complete set of adders,means to supply fluid under pressure to each said adder such that saidpiston and said cylinder are caused to move with respect to each otherto increase the length of said adder and said series, means to controltherate of operation of each of said adders, a flow control valvepositioned Within said second bore, means to supply fluid under pressureto said flow control valve means responsive to the length of said seriesto shift said flow control valve and fluid outlet passage means incommunication With said first bore and said second bore.

References Cited by the Examiner UNITED STATES PATENTS 465,477 12/1891Johnson 25158 XR 2,931,340 4/1960 White 91--167 3,000,363 9/1961 Hayneret al. 137625.64 3,130,549 4/1964 Freeman 91-167 XR 3,141,388 7/1964Brandstadter 91167 XR 3,216,454 11/1965 Richter et al. 137625.69

' FOREIGN PATENTS 483,835 4/ 1938 Great Britain.

M. CARY NELSON, Primary Examiner.

HENRY T. KLINKSIEK, Examiner.

1. A SERVO VALVE SUITABLE FOR OPERATING AN ACTUATOR COMPRISING A HOUSINGHAVING A BORE FORMED THEREIN, A PLURALITY OF CYLINDERS ARRANGED INEND-TO-END RELATIONSHIP SLIDABLY POSITIONED WITHIN SAID BORE FORMING ASERIES OF CYLINDERS, A PISTON RECIPROCALLY MOUNTED WITHIN EACH SAIDCYLINDER, A PISTON ROD ASSOCIATED WITH EACH PISTON EXTENDING FROM SAIDCYLINDER, AN INLET PASSAGE WITHIN SAID HOUSING ADAPTED TO RECEIVE FLUIDUNDER PRESSURE, MEANS CONNECTING SAID INLET PASSAGE TO SAID FIRST BORETO PROVIDE A BIAS AGAINST SAID SERIES, MEANS CONNECTING SAID INLETPASSAGE TO SAID FIRST BORE TO PROVIDE FOR ADMISSION OF FLUID WITHIN EACHSAID CYLINDER TO CAUSE RECIPROCATION OF SAID PISTON WITH RESPECT TO SAIDCYLINDER, A FLOW CONTROL VALVE